1. Field of the Invention
The present embodiments relate generally to light-emitting devices, and particularly to light-emitting device assemblies that include light-emitting diodes (LEDs) as light sources. The methods and systems of at least some of the embodiments include those that increase the removal of thermal energy generated by the device. Embodiments relate to managing the heat produced by high-output LEDs, so as to maintain optimal output performance without causing damage to the LED.
2. Description of the Prior Art
A light-emitting diode (LED) can often provide light in a more efficient manner than an incandescent light source and/or a fluorescent light source. The relatively high power efficiency associated with LEDs has created an interest in using LEDs to displace conventional light sources in a variety of lighting applications. For example, in some instances LEDs are being used as traffic lights, to illuminate displays systems and so forth. Many technological advances have led to the development of high power LEDs by increasing the amount of light emission from such devices.
Typically, an LED is formed of multiple layers, with at least some of the layers being formed of different materials. In general, the materials and thicknesses selected for the layers influence the wavelength(s) of light emitted by the LED. In addition, the chemical composition of the layers can be selected to promote isolation of injected electrical charge carriers into regions (commonly referred to as quantum wells) for relatively efficient conversion to optical power. Generally, the layers on one side of the junction where a quantum well is grown are doped with donor atoms that result in high electron concentration (such layers are commonly referred to as n-type layers), and the layers on the opposite side are doped with acceptor atoms that result in a relatively high hole concentration (such layers are commonly referred to as p-type layers).
LEDs also generally include contact structures (also referred to as electrical contact structures or electrodes), which are features on a device that may be electrically connected to a power source. The power source can provide current to the device via the contact structures, e.g., the contact structures can deliver current along the lengths of structures to the surface of the device within which energy can be converted into light.
The layers of semiconductor material of the LED are typically disposed on a supporting base. In certain LEDs, a layer of dielectric material is disposed between the multiple layers of semiconductor material and a thermally conductive substrate of the supporting base, such that the semiconductor material layers of the LED are electrically isolated from the thermally conductive substrate.
In some high power light-emitting devices, problems may arise with managing the thermal energies generated by the light-emitting devices, which may decrease the lifespan of the device. Managing the heat produced by LEDs has been a growing concern as newer designs and materials have allowed for increased output and size of LEDs, which often translates into an increase in the amount of heat produced. Much of this is a result of being able to drive LEDs with more electrical current. At times, one of the limiting factors preventing an LED from producing more lumen output is that of controlling the temperature of the LED itself. High temperatures can lead to deterioration or ultimately inoperability. Thus, dissipating heat both quickly and with increased capacity will allow for such LEDs to maintain high output, efficiency, and reliability. Accordingly, light-emitting devices and systems that effectively dissipate heat can be beneficial.
Weaving carbon fiber into Fire retardant material 4 (FR-4) such as Stablcor's ST325, placing heat shields around a plurality of LEDs, and providing higher thermal conducting metal substrates are some of the means others have attempted to solve the above stated problem. See for example published U.S. patent Applications 2009/0010010 A1, 2008/0258162 A1, 2008/0057333 A1, 2008/0258157 A1, 2009/026483 A1 and 2007/0010086. Other prior art exhibit large leads exiting an insulating body surrounding a copper slug such as U.S. Pat. No. 7,321,161.